1. Field of the Invention
The invention concerns a feed station for feeding a flat item individually or from a stack to a subsequent processing apparatus for the item. Such a flat item can be a thin mail piece such as a postcard, “normal” mail item of medium thickness (for example the “standard letter” in Germany) and thick mail pieces (for example as a “compact letter” in Germany). A mail piece is considered to be flat when it has a small thickness in comparison to the remaining dimensions of its format, situated in an x/y-plane of a Cartesian coordinate system. The feed station has a controller that controls the feed so that a high throughput is achieved. Such a feed station is used in connection with franking machines, addressing machines and other mail processing apparatuses.
2. Description of the Prior Art
Feeds of many different types are known in which the drive elements are mechanically coupled. Especially for short items, i.e. letters or mail pieces having a short format, separation drives are known that impress a drive force on a subsequent item that follows a current item very early so that the items are separated without large gaps therebetween or with an insufficient gap. Moreover, there is no possibility to vary these gaps within the feed.
A separation device from the company Neopost has two separation rollers and a transport device with one roller, with the rollers are all permanently kinematically coupled with one another. A sluice of the separation device is formed by a gap between the second separation roller and by a number of fingers at the head of a rocker. The gap has dimensions that correspond to a width and a height of filled, commercially available letter envelopes. A stack of mail pieces is placed on the first separation roller. As soon as the first separation roller releases the lowermost mail piece of the stack by its rotation, a transport force is immediately impressed by the first separation roller on a second lowermost mail piece. Different formats likewise have an influence on the separation. Although the separation device can be adapted to other formats by a mechanical displacement or adjustment, an automatic adaptation is not possible. Due to the lack of an additional sensor, no letter length measurement (and thus also no different control for different letter lengths) is possible. Additional disadvantages of the aforementioned separation device are that no gap monitoring (and thus also no optimization of the gaps) in the feed station is possible. The fixed kinematic coupling of the drive rollers does not allow a coordination of the separation velocity and/or the transport velocity, or a gap adjustment.
A franking system from Francotyp-Postalia GmbH has a feed station with a separation device and with a transport device, wherein—in the mail transport path—the feed station is arranged upstream in terms of mail flow of an Ultimail®-type franking machine. The separation device of the feed station has a transport belt in the pre-separation region. A drive drives the transport belt and the transport device, which are coupled with one another in terms of actuation. An additional drive acts on a separation roller. The sluice of the separation device is formed by a gap between the separation roller and by a number of fingers at the head of a rocker, which are arranged over the separation roller. It has been empirically established that the requirements for the reliability of the separation given a high throughput of flat items are satisfied with a high certainty only for a narrow spectrum (for example a defined type) of stacked mail goods. A sloped housing before the gap has a continuous tapering in the input region and causes compression of the mail pieces in the stack. Thick mail pieces cannot be separated from the stack if the gap through which a mail piece is sluiced has been set to be too narrow. However, if the gap has been set too wide, errors occur in the separation, in particular given a high throughput of flat items. The throughput likewise turns out to be less than maximum due to large gaps between the successive mail pieces, in particular given short mail pieces (postcards, for example). As soon as the lowermost mail piece releases (exits) the first separation roller by rotation of the transport belt, a transport force is impressed by the first separation roller on a respective second mail piece. This can likewise lead to separation errors. The surface friction value of the transport belt must be very exactly matched to the mail piece surface so that a propulsive force that is excessively strong is not impressed on the respective second lowermost mail piece of the stack. The reliability of the separation would be increased if a propulsive force acted only on the mail piece that should be separated and supplied.
A separation device for flat articles is known from DE10127993A1 that has a feed belt on driven deflection rollers and retention means. The retention means includes a separation element which with the feed belt forms a sluice via which the separated flat articles are transported along the entire length. The feed belt is designed as a segmented belt that has a pull-in segment and a sliding segment. Upon placement of a mail piece or stack of mail pieces, a first motor and a second motor are automatically activated by a controller when a first sensor detects the placement. The stack is transported to the retention means of the separation means as soon as the first motor is activated. The stack is separated by the lowermost mail piece being removed, and the second motor is controlled accordingly by the controller. An encoder electrically connected with the controller serves for the detection of the position reached by the pull-in segment and (via the controller) maintains the rotation speed constant of the second drive upon separation. The flat article can be pulled out from the separation device by rollers of an ejection device that are driven by a third motor and can subsequently be ejected from the separation device. The third motor is also controlled by the controller. In spite of a significant cost in motors, sensors and mechanical components, the separation device does not allow a predetermined gap to be maintained between successive flat articles, in particular mail pieces with varying thickness.
A franking system has different types of flat items such as postcards and letters of the C6, C6 long, B4 formats etc. However, the different flat letter items require different processing velocities during the separation if the separation should be achieved with a high probability. These velocities are then below the transition velocity from the feed station to a subsequent goods processing apparatus (a franking machine, for example). Gaps of different sizes thus arise between two successive flat items that can contribute to significantly reducing the throughput. Gaps of different size between successive flat items additionally result given different friction during their separation.